In the application of power electronic conversion technology, power devices are one of the most widely and frequently used electronic components. Power devices generate a large amount of heat during operation, so heat dissipation and temperature monitoring are required. If the heat sink is insufficient or the over-temperature protection circuit is unreliable, power device will be broken down by thermal, resulting in permanent failure of the power device.
Commonly used over-temperature protection circuits are based on thermistors or thermal temperature switches, and the temperature switches are widely used due to their simple structure, convenient use and simple protection circuit. In high-voltage and high-power applications, generally, multiple power modules share one heat sink. In this case, there is a problem of withstand voltage between a contact of the temperature switch and the outer casing. The withstand voltage problem is usually solved by using a high withstand voltage switch or adding an insulating ceramic sheet, but it has disadvantages such as increased cost or reduced temperature detection accuracy. Therefore, reducing the withstand voltage between the contact of the temperature switch and the outer casing is essential to ensure the reliable application of such temperature protection technology. In order to solve the problems of reducing the cost, increasing the temperature detection accuracy, and solving the withstand voltage between the contact of the temperature switch and the outer casing, it is urgent to improve the existing temperature protection circuit.